Recent advancement in antenna technology is expected to enable increasingly advanced antennas to be deployed in cellular radio networks. Antennas that are re-configurable in terms of beam-shape, so called re-configurable antenna systems (RAS) are already in use. Beam-forming and communication device beam-tracking is also gaining momentum. Further still, it is expected that large antennas comprising several hundreds individually controlled antenna elements will become available in near future.
Advanced antenna solutions are very promising but they also bring a set of new difficulties that will need to be addressed. A difficulty that may arise when the network nodes use antenna devices of different types is that uplink measurements made by different network nodes may give misleading results when compared, since the accuracy of the measurements may depend on the respective network node's antenna capabilities.
There may also be large systematic errors that are not accounted for when producing the measurements.
Further, calibration of e.g. antennas and receiving (RX) circuitry in a network node for obtaining accurate measurements is time-consuming and costly. Such calibration involves e.g. personnel going out to the site with measurement and calibration equipment. The calibration efforts may increase with the advancement degree of the antennas.
Calibration errors still further aggravates the comparisons of uplink measurements made by different network nodes by adding varying degree of calibration related errors to the measurements.